1. Field of the Invention
The present invention relates to a method for producing para-menthane-3,8-diol, and more particularly to a method for producing high-purity para-menthane-3,8-diol in high yield, effectively, and economically using citronellal as a raw material.
2. Prior Art
There are many diseases carried or caused by bloodsucking noxious insects, including ticks and mosquitoes, or other harmful living things. For example, mosquitoes cause malaria and yellow fever, fleas pest and eruption fever, and tsutsugamushi mites tsutsugamushi disease and others. Furthermore, even in case of not suffering such diseases, injuries of eruption, dermatitis and so on caused by mosquitoes, fleas, ticks and others are exceedingly heavy. Insecticides have been widely used for the prevention of the breeding and extermination of harmful living things including noxious insects from old times. However, there are some problems such as the appearance of tolerance to drugs due to misuse of insecticides, damages on human beings and animals from insecticides, and others. Moreover, under the present conditions, the prevention of the breeding and extermination of harmful living things can not be always done completely by insecticides.
Accordingly, instead of the prevention of the breeding and extermination of harmful living things, including noxious insects, through killing and wounding them, repellents which repel harmful living things to result in the prevention of the breeding and extermination of them have attracted public attention in recent years. Although various kinds of compounds, including para-menthane-3,8-diol, dialkyl phthalate and 2-ethyl-1,3-hexanediol, are known as compounds having the repellent action to noxious insects, among the compounds, para-menthane-3,8-diol is considered to be one of useful repellent compounds because of its high repellent action to noxious insects.
Para-menthane-3,8-diol is contained in leaves of eucalyptuses and can be obtained by extracting from leaves of eucalyptuses. However, extraction thereof from leaves of eucalyptuses is greatly restricted in points of raw material and the like, and it is difficult to obtain it in large quantities and economically. Consequently, methods for producing para-menthane-3,8-diol by chemical synthesis have been proposed. And in hitherto known methods of producing para-methane-3,8-diol,is as follows;
Citronellal is treated with aqueous sulfuric acid solution of 5 weight % (hereinafter referring to wt. %) in concentration at room temperature to cause the ring closure of citronellal. Then, after the reaction product is extracted with ether or toluene, para-menthane-3,8-diol is obtained by distilling the extract under reduced pressures (J. Am. Chem. Soc., 75, 2367 (1953), examined Japanese Patent Publication 3-80138 and U.S. Pat. No. 5,298,250).
However, in case where the above-mentioned usual method is used, the purity of obtained para-menthane-3,8-diol is low, and the yield of the para-menthane-3,8-diol is not sufficiently high. Because acetal substances which are dehydrated condensation products from para-menthane-3,8-diol and citronellal are produced as by-products in large quantities together with para-menthane-3,8-diol. Consequently, high-purity para-menthane-3,8-diol can not be obtained in high yield, effectively and economically.